The headlines coming out of last week’s arguments in Arizona v. United States have been focused on the likelihood that the Supreme Court will side with Arizona on its controversial SB 1070 law, four provisions of which have been prevented from going into effect by the lower federal courts because they were deemed likely to conflict with federal immigration law. But while it did seem like several justices—perhaps even a majority—did not see a preemption problem with the well-known “papers please” provision, there also appeared to be a majority of justices who were concerned about the other provisions of the law, including state criminal sanctions for aliens who do not carry registration documents and unauthorized migrants who seek work in Arizona.

Paul Clement, the conservative superstar Supreme Court lawyer who turned the rather improbable arguments in the healthcare lawsuits into a plausible case before the high court, spent most of his time before the Court last week attempting to soften the harsh image of SB 1070. He embraced Fourth Amendment limitations on arrests and detentions arising from the law. He denied that the state would continue to detain unauthorized migrants under SB 1070 if the federal government told local law enforcement officers the feds were not interested in deporting the undocumented immigrants (although I think this might be a misstatement if SB 1070’s criminal provision for failure to carry registration documents stays on the books). And, most of all, Clement argued again and again that Arizona was simply going along with federal immigration law in passing SB 1070, adopting federal standards as its own.

Solicitor General Don Verrilli effectively countered this argument with the Constitution’s text, history, and structure, echoing arguments made in the amicus briefs filed by Constitutional Accountability Center and a group of former government officials led by Madeleine Albright. The drafters of our Constitution, including James Madison and Alexander Hamilton, made it unmistakably clear that the federal government has the exclusive power to regulate immigration and consider the foreign policy implications of how we treat non-citizens within our borders. Verrilli argued that the enjoined provisions of SB 1070 were trumped by federal law under doctrines of field and conflict preemption.

This argument seemed more successful in some areas than others. As Justice Sotomayor commented at one point, his argument that verifying the immigration status of a person stopped by law enforcement officers under SB 1070 Section 2(b) “wasn’t selling very well.” Many observers have suggested that this meant that Justice Sotomayor wasn’t buying Verrilli’s argument, but I took her comment to be more about the feelings of her fellow Justices than a reflection of her own views. But more important, I think Verrilli’s argument that the “papers please” provision was preempted wasn’t “selling very well” only after several Justices established during Clement’s argument time that they could allow the “papers” provision to go into effect while continuing to block SB 1070’s state created criminal sanctions (for failure to carry registration documents and for seeking employment).

Without the bite of state criminal sanctions behind the status verification required/authorized by the “papers” provision, Chief Justice Roberts, and even Justice Breyer, seemed to have difficulty seeing how verifying immigration status and notifying the federal government that the state officers had encountered an undocumented person conflicted with federal law, when the decision of whether or not to initiate deportation remained with the feds. But I think some of those Justices might feel different if the state could prosecute undocumented immigrants under Section 3 of SB 1070, even if the federal authorities chose not to. At various points, different Justices sought to get the advocates to agree that the provisions could be considered separately.

Of course, things might not be as neat and clean as the Justices would like them to be. Even if the only provision to go into effect were Section 2b’s requirement that local law enforcement officers determine the immigration status of any person whom they stop or detain whenever “reasonable suspicion” exists that the person might be illegally present in the U.S., there are numerous complicating factors. First, verifying status is not always the simple task that Clement made it seem (about a 10 minute, task, he asserted). If you are a U.S. citizen by birth, but do not have a passport, there is no “database” that will quickly spit back a “legal” answer to the Arizona officer who has got you pulled over on the side of the road. Second, if you are not lawfully present, unless you have previously been caught in the immigration system, your name will not immediately come up with a clear “legal” or “illegal.” In short, the period of detention during which the local officers determine status could be quite significant (a matter of concern to both Justices Kennedy and Alito at argument).

Perhaps more important, in order to achieve SB 1070’s stated purpose of “attrition through enforcement,” local law enforcement officers would have to so aggressively pursue the “papers, please” provision that it creates such a hostile environment that individuals “self-deport.” This will inevitably draw many more people into SB 1070’s net than unauthorized migrants. While it is true, as Chief Justice Roberts emphasized before General Verrilli could get more than a word or two out of his mouth at last week’s argument, that the federal government’s case is based on preemption and not “racial profiling,” the Supreme Court has made clear that one of the reasons behind the need for “uniform” immigration policy is the desire to avoid harassment of citizens and non-citizens alike. As the Court held in Hines v. Davidowitz, the federal government has an interest in avoiding state laws that “permit[] invasion of the personal liberties of law-abiding individuals, or singl[e] out aliens as particularly dangerous and undesirable groups.” Stated another way, the federal government has a legitimate interest in creating a uniform immigration law that leaves immigrants “free from the possibility of inquisitorial practices and police surveillance.”

After last week’s argument, it seems highly possible that the Court could issue a split decision supporting some provisions of SB 1070 but not others. Section 3’s criminal sanction for failure to carry immigrant registration documents, as well as Section 5’s criminal penalties for undocumented migrants seeking work in Arizona, could remain enjoined. With the exception of Justice Scalia, and, presumably Justice Thomas, the rest of the Justices seemed to agree with General Verrilli that these provisions go beyond what federal law provides and conflict with Congress’s immigration policy choices. The fate of Section 6, which allows a law enforcement officer to, without a warrant, arrest a person the officer has “probable cause” to believe committed a public offense rendering him deportable, was less clear, although Justices Ginsburg, Kennedy, and Sotomayor all raised concerns about unreasonable detention.

Predicting what the Court will do based on oral argument is always a risky endeavor. But what the Court should do, as I have argued to the Court in an amicus brief in the Arizona case, is follow the Constitution and Court precedent and uphold the injunction against all of the provisions before the Court. SB 1070 is a single-minded, aggressive “attrition through enforcement” policy that directly conflicts with the Constitution’s delegation of immigration authority to the federal government. The nation’s Founders unmistakably gave the national government the power to speak for the United States on immigration matters and foreign affairs, and Arizona does not have the right to put in place its own “self-deportation” immigration policy.

But for now, all there is to do is wait until the Court rules, probably toward the end of June. (Or pass comprehensive immigration reform.)